Process for the production of end-capped nonionic surfactants

ABSTRACT

Process for the production of end-capped nonionic surfactants by forming an alcoholate between a fatty alcohol polyglycol ether and a solid base, reacting the alcoholate with a dialkyl sulfate, adding water to initiate phase separation, and separating the organic layer from the aqueous layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for the production of end-cappednonionic surfactants by forming an alcoholate between a fatty alcoholpolyglycol ether and a solid base, reacting the alcoholate with adialkyl sulfate and adding water to initiate phase separation.

2. Statement of Related Art

For a number of industrial processes, the presence of foam is extremelyundesirable. For example, both in the machine washing of beer or milkbottles and in the spray cleaning of automobile panels, not only is thecleaning or degreasing effect of the surface-active formulations used animportant factor, the avoidance of foam which can seriously interferewith the operation of machinery is of equal importance. This is all morethe so inasmuch as, in many cases, highly active but also high-foaminganionic surfactants are used.

The problem of controlling foam has been known for some time and,accordingly, various more or less convincing solutions to the problemare known from the prior art and may be divided into two groups.

The first group comprises processes involving the addition of defoamerswhich are often paraffinic hydrocarbons or silicone compounds. For thedescribed applications, however, this is mostly undesirable. The secondgroup of processes involve the use of surface-active formulations whichare themselves low-foaming and which may additionally exhibit defoamingproperties. The surfactants used are generally nonionic surfactants orsurfactant-like systems such as, for example, fatty alcohol propyleneglycol ethers or block polymers of ethylene and propylene glycol which,unfortunately, are not sufficiently biodegradable.

End-capped fatty alcohol polyglycol ethers, so-called "mixed ethers",which are described for example by R. Piorr in Fat. Sci. Technol. 89,106 (1987), have established themselves on the market as particularlyeffective low-foaming surfactants. These products are generallybutyl-end-capped nonionic surfactants which are known, for example, fromEP-A 0 124 815, EP-B 0 303 928, EP-B 0 324 340, EP-A 0 420 802, DE-A 3928 600 and DE-C 4 243 643.

Methyl mixed ethers occupy a special position. They are end-capped bymethyl groups and are normally obtained by reaction of the correspondingfatty alcohol polyglycol ethers with methyl halides U.S. Pat. No.4,587,365, BASF! or dimethyl sulfate.

In this connection, a one-pot process for the production of end-cappednonionic surfactants is known from EP 0 302 487 B1 (BASF). In thisprocess, fatty alcohol polyglycol ethers are reacted with dialkylsulfates in the presence of aqueous alkali metal hydroxides, thereaction taking place at a temperature in the range from 20° to 60° C.and the concentration of alkali metal hydroxide having to be kept above35% by weight, based on the aqueous phase, throughout the reaction.However, the products contain up to 25% by weight of unreacted startingproduct and are unacceptable from the point of view of color.

Accordingly, the problem addressed by the present invention was toprovide an improved process for the production of end-capped nonionicsurfactants of the methyl mixed ether type which would be distinguishedby a reduced content of unreacted starting material and by improvedcolor quality.

DESCRIPTION OF THE INVENTION

The present invention relates to a process for the production ofend-capped nonionic surfactants corresponding to formula (I): ##STR1##in which R¹ is an alkyl and/or alkenyl group containing 6 to 22 carbonatoms, n1 and n2 independently of one another stand for 0 or for numbersof 1 to 10 and m stands for numbers of 1 to 20, by reaction of alcoholalkoxylates with dialkyl sulfates, in which

(a) fatty alcohol polyglycol ethers corresponding to formula (II):##STR2## in which R¹, n1, n2 and m are as defined above, are reactedwith solid substantially water-free bases (III),

(b) the alcoholates formed are etherified with dialkyl sulfates (IV),

(c) water is added to the crude ethers in such a quantity that phaseseparation occurs and

(d) the organic valuable phases are removed by methods known per se.

A process in which alcoholate formation and etherification are carriedout in the presence of aqueous bases is already known from the priorart. However, it has surprisingly been found to be of far greateradvantage to carry out alcoholate formation and etherification in twostages and to use solid substantially water-free bases as reactantsbecause products with a relatively low content of unreacted startingmaterial can be obtained. In addition, the use of borohydrides in thealcoholate formation step leads to products with considerably improvedcolor quality.

Fatty alcohol polyglycol ethers

Fatty alcohol polyglycol ethers are known nonionic surfactants which maybe obtained by the relevant methods of preparative organic chemistry,for example by the addition of alkylene oxides to fatty alcohols.Depending on the alkoxylation catalyst, the ethers may have aconventional broad homolog distribution or a narrow homologdistribution.

Typical examples of fatty alcohol polyglycol ethers which may be used asstarting materials in accordance with the invention are products of theaddition of 5 to 15 moles of ethylene oxide and optionally 1 mole ofpropylene oxide to caproic alcohol, caprylic alcohol, 2-ethylhexylalcohol, capric alcohol, lauryl alcohol, isotridecyl alcohol, myristylalcohol, cetyl alcohol, palmitoleyl alcohol, stearyl alcohol, isostearylalcohol, oleyl alcohol, elaidyl alcohol, petroselinyl alcohol, linolylalcohol, linolenyl alcohol, elaeostearyl alcohol, arachyl alcohol,gadoleyl alcohol, behenyl alcohol and erucyl alcohol and the technicalmixtures thereof obtained, for example, in the high-pressurehydrogenation of technical methyl esters based on fats and oils oraldehydes from Roelen's oxosynthesis and as monomer fraction in thedimerization of unsaturated fatty alcohols.

Particularly preferred starting materials are fatty alcohol polyglycolethers corresponding to formula (II) in which R¹ is an alkyl groupcontaining 12 to 18 carbon atoms, n1 stands for 0, m stands for numbersof 5 to 15 and n2 stands for the number 1 or in which R¹ is an alkylgroup containing 6 to 10 carbon atoms, n1 stands for the number 1, mstands for numbers of 5 to 15 and n2 has a value of 0.

Bases

Suitable bases are primarily the oxides, hydroxides and carbonates ofthe alkali and/or alkaline earth metals. Typical examples are lithiumhydroxide, sodium carbonate, sodium hydrogen carbonate, magnesium oxide,magnesium hydroxide, calcium oxide and calcium hydroxide. It ispreferred to use sodium hydroxide and/or potassium hydroxide, preferablypotassium hydroxide. The bases are used in the form of solid products,i.e. for example beads, flakes or pellets, and generally have a watercontent from their production of less than 15% by weight and, moreparticularly, less than 10% by weight. A water content of this order istolerable in the process according to the invention although, basically,water-free products (which unfortunately are not readily available on anindustrial scale) would be preferred.

It has been found to be of advantage to use the fatty alcohol polyglycolethers (II) and the bases (III) in a molar ratio of 1:1.0 to 1:1.5 andpreferably in a molar ratio of 1:1.1 to 1:1.4.

Alcoholate formation

The step in which the alcoholate is formed is normally carried out at atemperature of 20° to 98° C. and preferably at a temperature of 40° to80° C. In one preferred embodiment of the invention, alkali metal and/oralkaline earth metal borohydrides are added to the fatty alcoholpolyglycol ethers, which leads to substantially colorless products.Typical examples of suitable borohydrides are potassium borohydride,magnesium borohydride and, in particular, sodium borohydride. Othersuitable stabilizers are lithium alanate and hypophosphorous acid andalkali metal salts thereof which may even be used in combination withsodium borohydride. The borohydrides are normally used in quantities of100 to 1000 ppm and, more particularly, in quantities of 300 to 700 ppm,based on the fatty alcohol polyglycol ethers.

Dialkyl sulfates

In the context of the invention, dialkyl sulfates are understood to bediethyl sulfate and, in particular, dimethyl sulfate. Basically,mixtures of dimethyl and diethyl sulfate and higher alkyl sulfates(providing they are available in commercial quantities) may also be usedas alkylating agents for the process according to the invention. Thefatty alcohol polyglycol ethers (II) and the dialkyl sulfates (IV) arepreferably used in a molar ratio of 1:1.0 to 1:1.5 and, moreparticularly, in a molar ratio of 1:1.1 to 1:1.4.

Etherification

The etherification step is advantageously carried out at a lowertemperature than the alcoholate formation. A temperature in the rangefrom 20° to 100° C. and, more particularly, in the range from 40° to 50°C. has proved to be optimal.

Phase separation and aftertreatment

The aftertreatment of the crude alkylation products with water has twoobjectives. Firstly, the quantity of inorganic salt formed during theetherification step migrates into the water phase and, secondly,unreacted dialkyl sulfate is decomposed. To this end, it has proved tobe of advantage to carry out the phase separation at a temperature of70° to 98° C. After phase separation, the ether is normally dried andunreacted base is filtered off. If necessary, the content of freealkylating agent can be further reduced by adding 0.1 to 1% by weight ofan amino compound, for example ammonia, glycine or an alkanolamine, tothe ether, if desired even before phase separation.

Commercial Applications

The end-capped nonionic surfactants obtainable by the process accordingto the invention are distinguished by excellent wetting power, areextremely low-foaming and are capable in particular of defoamingformulations containing anionic surfactants. Accordingly, they areparticularly suitable for the production of machine bottle washingdetergents in which they may be present in quantities of 1 to 50% byweight and preferably in quantities of 5 to 35% by weight, based on thedetergent.

The following Examples are intended to illustrate the invention withoutlimiting it in any way.

EXAMPLES Examples 1 to 4

500 g of C_(12/14) cocoalcohol+6 EO and 500 ppm of sodium borohydride,based on the polyglycol ether, were introduced into a three-necked flaskequipped with a dropping funnel, stirrer and reflux condenser and alkalimetal hydroxide flakes were added in portions with intensive stirringover a period of 2 hours at a temperature of 80° C. The alcoholatemixture was then cooled to 45° C. and, after the addition of dimethylsulfate, was stirred first for 1 hour at 45° C., then for 2 hours at 50°C. and, finally, for 1 hour at 60° C. 500 g of water were then added,the mixture was heated to 80°-85° C. and was stirred for another 2 hoursduring which separation occurred. The sulfate salt formed beingdissolved almost completely in the aqueous phase. After phaseseparation, the organic useful-material phase was dried in vacuo andthen filtered. Particulars of the quantity ratios used and thecharacteristic data of the products can be found in Table 1 where thepercentages shown are percentages by weight.

Example 5

Example 1 was repeated using octanol+1 PO+10 EO. The results are set outin Table 1.

Example 6

Example 1 was repeated using C_(12/14) cocofatty alcohol+10 EO+1 PO. Theresults are set out in Table 1.

Comparison Example C1

Example 1 was repeated except that no sodium borohydride was added inthe alcoholate formation step. The results are set out in Table 1.

Comparison Example C2

Example 1 was repeated using a corresponding quantity of 50% by weightpotassium hydroxide solution instead of the KOH flakes and leaving outthe sodium borohydride. The results are set out in Table 1.

                  TABLE 1                                                         ______________________________________                                        Etherification with Dimethyl Sulfate                                                                       Yield    Salt Color                              Ex.  Base    F:Base    F:DMS % of Th. %    Gard.                              ______________________________________                                        1    KOH     1:1.27    1:1.15                                                                              95       <1   <1                                 2    KOH     1:1.30    1:1.20                                                                              95       <1   <1                                 3    KOH     1:1.40    1:1.30                                                                              94       <1   <1                                 4    NaOH    1:1.30    1:1.20                                                                              93       <1   <1                                 5    KOH     1:1.27    1:1.15                                                                              95       <1   <1                                 6    KOH     1:1.27    1:1.15                                                                              91       <1   <1                                 C1   KOH     1:1.27    1:1.15                                                                              95       <1   11                                 C2   KOH     1:1.27    1:1.15                                                                              76       <1   Red                                ______________________________________                                         Legend:                                                                       F:base = Molar ratio of fatty alcohol polyglycol ether to base                F:DMS = Molar ratio of fatty alcohol polyglycol ether to dimethyl sulfate     Salt = Content of inorganic sulfate in the product                            Color = Gardner color number                                             

We claim:
 1. A process for the production of end-capped nonionicsurfactants corresponding to formula (I): ##STR3## in which R¹ is analkyl or alkenyl group containing 6 to 22 carbon atoms, n1 and n2independently of one another are 0 or a number of from 1 to 10, and m isa number of from 1 to 20, comprising the steps ofA) reacting at leastone fatty alcohol polyglycol ether corresponding to formula (II):##STR4## in which R¹, n1, n2 and m are as defined above, with a solidbase (III), having a water content of less than 15% by weight, in thepresence of an alkali metal borohydride, an alkaline earth metalborohydride, or both; B) etherifying the resulting alcoholate oralcoholates with dimethyl sulfate, C) adding water to the etherifiedalcoholate or alcoholates in an amount sufficient to result in phaseseparation into an organic phase and an aqueous phase; and D) separatingthe organic phase from the aqueous phase.
 2. The process of claim 1wherein in formula II, R¹ is an alkyl group containing from 12 to 18carbon atoms, n1 is 0, m is a number of from 5 to 15, and n2 is
 1. 3.The process of claim 1 wherein in formula II, R¹ is an alkyl groupcontaining 6 to 10 carbon atoms, n1 is 1, m is a number of from 5 to 15,and n2 is
 0. 4. The process of claim 1 wherein in step A) the solid baseis sodium hydroxide, potassium hydroxide, or both.
 5. The process ofclaim 1 wherein the ether of formula II and the solid base (III) arepresent in a molar ratio of from about 1:1 to about 1:1.5.
 6. Theprocess of claim 1 wherein step A) is carried out at a temperature inthe range of from about 20° to about 98° C.
 7. The process of claim 1wherein in step B) the alcoholate or alcoholates and the dimethylsulfate are present in a molar ratio of from about 1:1 to about 1:1.5.8. The process of claim 1 wherein step B) is carried out at atemperature in the range of from about 20° to about 100° C.
 9. Theprocess of claim 1 wherein step C) is carried out at a temperature inthe range of from about 70° to about 98° C.
 10. The process of claim 1wherein in step A) the solid base is an oxide, hydroxide, or carbonateof an alkali or alkaline earth metal.
 11. The process of claim 1 whereinin step A) the solid base has a water content of less than 10% byweight.
 12. The process of claim 5 wherein said molar ratio is fromabout 1:1.1 to about 1:1.4.
 13. The process of claim 1 wherein in stepA) the borohydride is sodium borohydride, potassium borohydride, ormagnesium borohydride.
 14. The process of claim 1 wherein theborohydride is present in from about 100 to about 1000 ppm. based on theat least one ether of formula II.
 15. The process of claim 14 whereinthe borohydride is present in from about 300 to about 700 ppm.
 16. Theprocess of claim 6 wherein said temperature is in the range of fromabout 40° to about 80° C.
 17. The process of claim 8 wherein saidtemperature is in the range of from about 40° to about 50° C.
 18. Theprocess of claim 1 wherein in step A) the solid base is sodiumhydroxide, potassium hydroxide, or both; the ether of formula II and thesolid base (III) are present in a molar ratio of from about 1:1 to about1:1.5; the borohydride is present in from about 0.1 to about 1% byweight, based on the at least one fatty alcohol polyglycol ether; stepA) is carried out at a temperature in the range of from about 20° toabout 98° C.; in step B) the alcoholate or alcoholates and the dimethylsulfate are present in a molar ratio of from about 1:1 to about 1:1.5;step B) is carried out at a temperature in the range of from about 20°to about 100° C.; and step C) is carried out at a temperature in therange of from about 70° to about 98° C.
 19. The process of claim 18wherein in formula II, R¹ is an alkyl group containing from 12 to 18carbon atoms, n1 is 0, m is a number of from 5 to 15, and n2 is 1, orwherein in formula II, R¹ is an alkyl group containing 6 to 10 carbonatoms, n1 is 1, m is a number of from 5 to 15, and n2 is
 0. 20. Theprocess of claim 18 wherein in step A) the solid base is sodiumhydroxide, potassium hydroxide, or both; the borohydride is sodiumborohydride, potassium borohydride, or magnesium borohydride, and theborohydride is present in from 100 to 1000 ppm, based on the at leastone ether of formula II.